The Wikipedia page for 1973's Battles Without Honour and Humanity (仁義なき戦い), the first in a famous series of yakuza films, says the film is "often called the 'Japanese Godfather'." The single source cited for this assertion is a one paragraph review that mentions the comparison briefly in order to say it's inaccurate. Though the review considers this a positive point, apparently believing the Japanese film displays greater realism, I would argue the two are certainly different but realism has nothing to do with it. The Godfather is filled with memorable characters and effective family drama while Battles Without Honour and Humanity features a collection of character types with leads played by a few remarkably handsome and rugged men. The film doesn't quite rise above a loving celebration of the genre established over the fifteen or so years preceding it, revelling in typical plot turns and deliberately invoking typical plot mechanics. Seijun Suzuki's Tokyo Drifter, released a few years earlier, almost feels like a parody of this film, so sincerely does Battles without Honour and Humanity devote itself to well worn devices, despite the fact that the film is supposedly based on a true story. But it has some nice bits of style and the actors are attractive.
This is my favourite shot in the film--the film's hero, Hirono (Bunta Sugawara), having sex with a prostitute and revealing to us in the process his massive fish tattoo. This is his last taste of freedom before he assassinates a rival yakuza boss at the behest of his own comically weak and sobbing boss, Yamamori (Nobuo Kaneko). I can imagine what Don Corleone would say about him.
Yamamori promises to make Hirono his heir after the long prison sentence. The protagonist going to prison for a hit reminds one of Pale Flower while the soldier's admirable loyalty to his unworthy boss is reminiscent of a number of yakuza films, most notably Tokyo Drifter.
Bunto Sugawara as Hirono is certainly an exceptionally good lead, charismatic and rugged. I'd like to see him in some more action films but his character is a bit weightless here. His loyalty doesn't feel very natural and then instances of his disloyalty feel less so.